The closed form expressions for the expected value and variance of the PPO derived in Section  facilitate the comparison of various popular geometries in ways that were not previously possible. In temporal spectral estimation, where the windows are uniform, the expected value of the PPO is the convolution of the true PSD with the Fourier transform of a Bartlett window [1]}. When the main lobe width (MLW) of the Bartlett window is significantly narrower than the narrowest peak in the true PSD, the PPO is approximately unbiased even for a colored process [2]}, [1]}.
